This invention lies in the field of golf clubs and methods of producing coordinated sets. It is more particularly directed to the type of clubs commonly known as "irons" and to a new and different relation between the various irons in any given set.
High quality irons are made and marketed in "matched" sets which are intended to assist a golfer in achieving uniformly good playing ability with all of the clubs rather than a few favorite ones which seen best suited to him. A widely held theory is that such matching consists in providing the same feel or "swing weight" with each club. In a conventional set, such as eight clubs ranging from a long distance No. 2 to a short distance No. 9, the total length of each successive club is shorter by about one half inch than the preceding club and the head weight is progressively increased by a small amount as the length is decreased to achieve the desired constant swing weight.
While swing weight is not a concrete term there are two generally accepted ways of measuring it which produce consistent results on arbitrary scales. One system determines the static moment of a club and is disclosed in U.S. Pat. No. 1,953,916, issued to R. W. Adams. In this patent, a club is mounted on a beam scale so that the grip is supported in cantilever fashion over the beam with a fulcrum at a constant distance in from the grip end of the club, such as about 14 inches, with the head spaced away from the scale. The head consequently produces a substantial overbalance, and a poise is moved along the beam to obtain a balance. At this point, the reading on the beam, marked to an arbitrary scale, represents the swing weight of the club. These readings may for example be units denoted DO (zero), D1, D2 etc. to as high a figure as needed. If the reading for a first club is D2 and for a second club is D1, then the head weight of the second club may be increased until the swing weight is D2. The same procedure may be followed with an entire set so that they will all have the same D2 swing weight.
Another system of comparative measurement the prior art discloses, a club mounted on the table of a torsional pendulum and its moment of inertia is determined. Other clubs are mounted in the same way and measured. Similarly, the head weights may be increased, or decreased as required to obtain the same moment of inertia throughout the set. Although the prior art reference contends that the dynamic moment reading gives better results than the static moment reading because golf clubs are used in a dynamic way, it has been found that the results of both systems are close enough to achieve their intended result of fairly constant swing weight. No consideration is given by either of them to any relation of the flexibilities of the clubs in a set.
Another prior art reference discloses the idea of varying the stiffness of the shafts, using the most flexible shafts with the lowest numbered irons and the least flexible shafts with the highest numbered irons, with the flexibility varying on a logarithmic scale. He gives no consideration to any relation between the head weights or the swing weights of the clubs in a set.
It has been found that although sets having constant swing weights and sets having predetermined variations of flexibility are far more satisfactory than haphazardly arranged unmatched sets, they still leave much to be desired. Assumimg that a given golfer has found a set in which the middle distance irons seem to be well suited to his style and ability, he will find that the others do not seem to be right for his purposes. His actual trouble is that, with such a set, the lower numbered irons are too heavy and stiff for him and the higher numbered irons are too flexible and light.